Coral Bleaching and Disease

Coral bleaching and disease have become central topics of discussion among coral reef managers, scientists, and the general public,
largely because of the alarming rate at which these threats have increased in the last two decades. For example, coral bleaching, once
thought to be a localized phenomenon affecting selected reefs in the Caribbean, eastern Pacific, and Indonesia, is now documented
and considered as a major threat to all major coral reef ecosystems worldwide.

Since 1979, nine major coral bleaching episodes have affected important coral reef provinces around the world, with an alarming
reported increase in scale and intensity in recent years. Mass coral bleaching has resulted in significant losses of live coral cover
globally, with an estimated 16% mortality of the world's reef corals during the 1997–98 bleaching episode. This episode is the
most geographically extensive and severe on record. Because reef-building corals provide much of the primary productivity and
topographic complexity of the ecosystem, alterations in the abundance and diversity of corals severely affect the majority of other reef
dwelling organisms, including fishes, algae, and non-coral invertebrates. As such, the socioeconomic ramifications of mass coral
bleaching to coastal communities can be long-lasting and severe, with potential detrimental effects to fish stocks, coastal erosion,
and tourism.
NOAA's Coral Reef Watch
has developed metrics that link satellite-derived sea-surface temperatures and coral bleaching, as well as tools that provide near
real-time monitoring of environmental conditions and identify areas at risk of mass coral bleaching. Timely monitoring of sea-surface
temperature provides researchers and managers with tools to better understand and better address the complex interactions and potential
effects of mass coral bleaching.

Likewise, back in the 1970s and 1980s, coral diseases were considered to be a problem limited to Caribbean reefs, with some localized outbreaks in
the Red Sea, attributable mainly to land-based sources of pollution. Since 1990, however, significant disease outbreaks and associated dramatic coral losses have been
reported within all reef systems worldwide, with significant events occurring in the Great Barrier Reef between 2001 and 2003 and
Caribbean-wide in 2005.

Coral bleaching and disease are health impairments that interfere and modify a coral's ability to perform normal physiological
functions (maintenance, growth, and reproduction). They typically are caused by a suite of agents: environmental factors, such as
nutrients, toxicants, and climate; pathogens, including bacteria and viruses (infectious agents); and inherent or congenital defects
(Wobeser 2006). CRED's
Pacific RAMP
conducts long-term, broad-scale assessment and monitoring of coral bleaching and disease to document the prevalence of these health
conditions on U.S. Pacific reefs and investigate the factors that may be contributing to their occurrence. Since 2006, and with direct
support from
NOAA's Coral Reef Conservation Program
CRED conducts routine coral bleaching disease surveys at the Remote Pacific Island Areas, American Samoa, the main Hawaiian Islands,
the Northwestern Hawaiian Islands, Guam, and the Commonwealth of the Northern Mariana Islands (CNMI). Bleaching and disease prevalence
estimates, for which no data existed in many of the U.S. Pacific jurisdictions prior to this project (e.g., Howland, Baker, and Jarvis
Islands, Kingman Reef, Wake Atoll, and the CNMI), is now better characterized, and a better understanding of disease occurrence and
potential effects on U.S. Pacific coral reefs is emerging. These activities support the goals and objectives of the Coral Reef
Conservation Program's
National Coral Reef Monitoring Plan,
which is aimed at assessing the status and trends of the corals and coral reef ecosystems of the United States.